Response of Savanna Fire Regimes to Changing Fire‐Management Policies in a Large African National Park

Abstract

Approaches to fire management in the savanna ecosystems of the 2-million ha Kruger NationalPark, South Africa, have changed several times over the past six decades. These approaches have included regular and flexible prescribed burning on fixed areas and a policy that sought to establish a lightningdominated fire regime. We sought to establish whether changes in management induced the desired variability in fire regimes over a large area. We used a spatial database of information on all fires in the park between 1957 and 2002 to determine elements of the fire regime associated with each management policy. The area that burned in any given year was independent of the management approach and was strongly related to rainfall (and therefore grass fuels) in the preceding 2 years. On the other hand, management did affect the spatial heterogeneity of fires and their seasonal distribution. Heterogeneity was higher at all scales during the era of prescribed burning, compared with the lightning-fire interval. The lightning-fire interval also resulted in a greater proportion (72% vs. 38%) of the area burning in the dry season. Mean fire-return intervals varied between 5.6 and 7.3 years, and variability in fire-return intervals was strongly influenced by the sequencing of annual rainfall rather than by management. The attempt at creating a lightning-dominated fire regime failed because most fires were ignited by humans, and the policy has been replaced by a more pragmatic approach that combines flexible prescribed burning with lightning-ignited fires.Respuesta de los Regimenes de Fuegos de Sabana a Cambios en las Políticas de Gestión de Fuego en un Parque Nacional Africano Resumen: Durante las seisúltimas décadas, los métodos de gestión de fuego en los ecosistemas de sabana han cambiado varias veces en el Parque Nacional Kruger (2 millones de ha), Sudáfrica. Estos métodos incluyeron quemas prescritas regulares y flexibles enáreas determinadas y una política que buscaba establecer un régimen de fuego dominado por relámpagos. Buscamos establecer si los cambios de gestión indujeron la variabilidad deseada en los regimenes de fuego en unárea extensa. Utilizamos una base de datos espacial de la informaciónde todos los incendios en el parque entre 1957 y 2002 para determinar elementos del régimen de fuego asociados con cada política de gestión. Elárea quemada en cualquier año fue independiente del método de gestión y se relacionaba cercanamente con la precipitación pluvial (y por lo tanto con pastos combustibles) en los dos años precedentes. Por otro lado, la gestión afectó a la heterogeneidad espacial de los incendios y su distribución estacional. En comparación con el intervalo de fuego por relámpagos, la heterogeneidad fue mayor en todas las escalas durante el período de quemas prescritas. El período de fuego por relámpagos también presentó una mayor proporción (72% vs. 38%) deárea quemada durante laépoca de secas. Los intervalos promedio de retorno de fuego variaron entre 5.6 y 7.3 años, y la secuencia de la precipitación anua...

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